diff --git a/Tests/AntiFraudTests.cs b/Tests/AntiFraudTests.cs
index 584419c..8ac6f2d 100644
--- a/Tests/AntiFraudTests.cs
+++ b/Tests/AntiFraudTests.cs
@@ -45,7 +45,7 @@ public void TestGetAntiFraudHeaders() {
     [Fact]
     public void TestGetPropertiesForMethod() {
       var props = AntiFraud.AntiFraud.GetPropertiesForMethod(ConnectionMethod.DESKTOP_APP_DIRECT);
-      Assert.Equal(12, props.Count());
+      Assert.Equal(14, props.Count());
     }
   }
 }
diff --git a/Tests/TestBase.cs b/Tests/TestBase.cs
index 826abcf..b1cd933 100644
--- a/Tests/TestBase.cs
+++ b/Tests/TestBase.cs
@@ -73,10 +73,13 @@ protected Client GetClient() {
       client.AntiFraud.PopulateLocalIPs();
       client.AntiFraud.PopulateMACAddresses();
       client.AntiFraud.PopulateUserAgent();
+      client.AntiFraud.VendorForwarded = new Forwarded[] {
+        new Forwarded { By = System.Net.IPAddress.Parse("8.8.8.8"), For = System.Net.IPAddress.Parse("fe80::21a6:9255:4c0b:78e4%14")}
+      };
 
       // Even though the documentation states that that these are optional, the API returns an error
       client.AntiFraud.UserAgent.DeviceManufacturer = "Dell";
-      client.AntiFraud.UserAgent.DeviceModel = "XPS";
+      client.AntiFraud.UserAgent.DeviceModel = "XPS Gaming PC";
 
       client.AntiFraud.MultiFactor = new[] {
         new MultiFactor() {
diff --git a/TipsTrade-HMRC/AntiFraud/AntiFraud.cs b/TipsTrade-HMRC/AntiFraud/AntiFraud.cs
index a621fd7..2acdefe 100644
--- a/TipsTrade-HMRC/AntiFraud/AntiFraud.cs
+++ b/TipsTrade-HMRC/AntiFraud/AntiFraud.cs
@@ -230,7 +230,7 @@ private Dictionary<string, string> GetAntiFraudHeaders(List<string> errors) {
 
         string headerValue;
         if (value is string str) {
-          headerValue = str; // string are enumerable so catch them here
+          headerValue = HttpUtility.UrlEncode(str); // string are enumerable so catch them here
 
         } else if (value is IDictionary dict) {
           var sb = new StringBuilder();
diff --git a/TipsTrade-HMRC/AntiFraud/Forwarded.cs b/TipsTrade-HMRC/AntiFraud/Forwarded.cs
index fd5562d..677a48b 100644
--- a/TipsTrade-HMRC/AntiFraud/Forwarded.cs
+++ b/TipsTrade-HMRC/AntiFraud/Forwarded.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Net;
+using System.Web;
 
 namespace TipsTrade.HMRC.AntiFraud {
   /// <summary>Represents an object that contains information on hops over the internet that terminate TLS.</summary>
@@ -15,7 +16,7 @@ public string GetHeaderValue() {
       if (By == null) throw new InvalidOperationException($"The {nameof(By)} property cannot be null.");
       if (For == null) throw new InvalidOperationException($"The {nameof(For)} property cannot be null.");
 
-      return $"by={By}&for={For}";
+      return $"by={HttpUtility.UrlEncode(By.ToString())}&for={HttpUtility.UrlEncode(For.ToString())}";
     }
   }
 }
diff --git a/TipsTrade-HMRC/AntiFraud/UserAgent.cs b/TipsTrade-HMRC/AntiFraud/UserAgent.cs
index c124421..f7c4ab6 100644
--- a/TipsTrade-HMRC/AntiFraud/UserAgent.cs
+++ b/TipsTrade-HMRC/AntiFraud/UserAgent.cs
@@ -10,7 +10,7 @@ public class UserAgent : IAntiFraudValue {
 
     /// <summary>Gets or sets the device model.</summary>
     public string DeviceModel { get; set; }
-    
+
     /// <summary>Gets or sets the operating system family.</summary>
     public string OSFamily { get; set; }
 
@@ -20,10 +20,10 @@ public class UserAgent : IAntiFraudValue {
     /// <summary>Retuns a string that contains the anti fraud header value.</summary>
     public string GetHeaderValue() {
       var dict = new Dictionary<string, string> {
-        {"os-family", OSFamily },
-        {"os-version", OSVersion },
-        {"device-manufacturer", DeviceManufacturer },
-        {"device-model", DeviceModel }
+        {"os-family", HttpUtility.UrlEncode(OSFamily) },
+        {"os-version", HttpUtility.UrlEncode(OSVersion) },
+        {"device-manufacturer", HttpUtility.UrlEncode(DeviceManufacturer) },
+        {"device-model", HttpUtility.UrlEncode(DeviceModel) }
       };
 
       return dict.GetHeaderValue();